massive: move a lot of things

25-functions-and-pointers/02-basics/main.go

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+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+//
+// You need run this program like so:
+//   go run .
+//
+// This will magically pass all the go files in the current directory to the
+// Go compiler.
+//
+//
+// BUT NOT like so:
+//   go run main.go
+//
+// Because, the compiler needs to see global.go too
+// It can't magically find global.go — what you give is what you get.
+//
+
+package main
+
+import (
+	"fmt"
+	"strconv"
+)
+
+func main() {
+	local := 10
+	show(local)
+
+	incrWrong(local)
+	fmt.Printf("local → %d\n", local)
+
+	// incr(local)
+	local = incr(local)
+	show(local)
+
+	local = incrBy(local, 5)
+	show(local)
+
+	_, err := incrByStr(local, "TWO")
+	if err != nil {
+		fmt.Printf("err   → %s\n", err)
+	}
+
+	local, _ = incrByStr(local, "2")
+	show(local)
+
+	// CHAINING
+
+	// can't save the number back into main's local
+	show(incrBy(local, 2))
+	show(local)
+
+	// can't pass the results of the multiple-value returning func
+	// show(incrByStr(local, "3"))
+
+	// can call showErr directly because it accepts the same types
+	// of parameters as with incrByStr's result values.
+	// local = sanitize(incrByStr(local, "NOPE"))
+	// show(local)
+
+	local = sanitize(incrByStr(local, "2"))
+	show(local)
+
+	local = limit(incrBy(local, 5), 2000)
+	show(local)
+}
+
+func show(n int) {
+	// can't access main's local
+	// fmt.Printf("show : n = %d\n", local)
+	fmt.Printf("show  → n = %d\n", n)
+}
+
+// wrong: incr can't access to main's `local`
+func incrWrong(n int) {
+	// n := local
+	n++
+	// can't return (there are no result values)
+	// return n
+}
+
+func incr(n int) int {
+	n++
+	return n
+}
+
+func incrBy(n, factor int) int {
+	return n * factor
+}
+
+func incrByStr(n int, factor string) (int, error) {
+	m, err := strconv.Atoi(factor)
+	n = incrBy(n, m)
+	return n, err
+}
+
+func sanitize(n int, err error) int {
+	if err != nil {
+		return 0
+	}
+	return n
+}
+
+func limit(n, lim int) (m int) {
+	// var m int
+	m = n
+	if m >= lim {
+		m = lim
+	}
+	// return m
+	return
+}